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Date: Tue, 12 Jan 1999 23:45:32 +0000
From: Karl Pielorz <kpielorz@tdx.co.uk>
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To: Bruce Evans <bde@zeta.org.au>
CC: current@FreeBSD.ORG, kjc@csl.sony.co.jp
Subject: Re: HZ missing in options?
References: <199901122336.KAA11327@godzilla.zeta.org.au>
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Bruce Evans wrote:
> 
> >Is there any reason why HZ isn't listed in sys/conf/options?
> >Or just an oversight?  If so, I'll add the following line.
> 
> Changing it used to break xntpd's kernel PLL.  Increasing it used to
> significantly increase the potential inaccuracy of the clock (from
> 50 ppm for 100 Hz to 500 ppm for 1000 Hz).  Increasing it is still
> harmful for adjtime(2).  This shouldn't be a problem except when xntpd
> is misconfigured to use adjtime() instead of the kernel PLL.

Does anyone know if this still does break things? - We have a few machines
here running 1000Hz... It helps with things like AltQ / DummyNet etc.

The Cyclades serial ports we have also seem to require it for polled mode (I
guess understandbly), but we seem to get away without it (probably because
they're not loaded much).

-Kp

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